In a carrier of a catalyst, or an artificial bone, an artificial dental root (hereinafter, referred to as an implant member) for artificial biomaterial transplantation, a porous layer having a porous structure is formed on the surface in order to increase a surface area.
As a method for forming a porous layer having a porous structure on a surface, the following two methods have been used, that is, (1) a method carrying out a laser beam machining on the surface of a metallic body (or an alloy body), and (2) a method piling up thin sheets made with metallic materials having many pores while three-dimensionally controlling a hole shape in the porous structure, which is described in Japanese Patent Application Laid-Open No. H10-155823.
Incidentally, as for the manufacturing method (1), although the metallic body (or the alloy body) having a porous structure only on the surface, that is, a rough surface, can be easily obtained, there was the problem that a porous layer having a three-dimensional porous structure cannot be obtained. Further, in the case of a metal (or an alloy) having high melting point, there were problems that a high output laser beam machine and a long processing time were necessary for the laser beam machining.
Further, as for the manufacturing method (2), although a porous layer having a three-dimensional porous structure could be formed, there were problems that it took the time and effort for controlling the pore shape and that a long time was necessary for manufacturing.
Thus, it is desired that the above-mentioned porous layer is made by a casting method capable of comparatively easy manufacture. When a porous article is manufactured by the casting method, projections formed on an inner surface of a mold constitute pores of a porous article. However, in order to take out a cast body from the mold, the head of each projection must be narrower than its base. Therefore, as for the pore shape of the porous article obtained by the casting method, a bottom part of the pore is narrower than an opening part of the hole. As a result, for example, one like a golf ball having a concave dimple on the surface could be cast, but there was a problem to make a cast article having a complicated three-dimensional porous structure on the surface by casting.
The present invention solves the above-mentioned problems, and the primary objective is to provide a method for manufacturing a mold, wherein a porous body can be made.